What makes Sumo so mean?

Sumo is my boy cat. He is usually very loving and affectionate to me, but his mean side comes out when he hunts. He has learned that if he brings his prey (usually mice and lizards) in the house and puts them in the bathtub, they can't get away and he can kill them at his leisure. 

Unfortunately, he hasn't figured out that this tactic doesn't work on birds. Many times I have come home from work to find a pissed-off blue jay perched on the shower rod. Oh, and Sumo's also not very nice to his "sister" Murphy. He often slaps her around or attacks her for no apparent reason. I think he does it just to hear her screech. Murphy definitely thinks Sumo is a meankitty.

Photo submitted by: Anonymous
Date last updated: 10/25/05